1. Field of the present invention
The present invention relates to a carbon-porous media composite electrode material, a composite electrode using the same, and a preparation method thereof.
2. Description of the Background Art
A capacitive deionization (hereinafter, referred to as ‘CDI’) processing apparatus is an apparatus that removes ions present in a solution by electrochemically adsorbing them onto an electrode surface. As an active material of an electrode for capacitive deionization process, used are activated carbon, carbon aerogel, carbon nanotube, etc.
Carbon aerogel has been known as an ideal material for a CDI electrode because it has a high specific surface area (from 400 to 1100 m2/g), a low electric resistance (400 mΩ/cm) and a nano-sized porous structure, and because its pores are connected to one another, its pore size and density can be adjustable, and its electric conductivity is excellent. Besides, its preparation process is simple and its capacitance is very excellent. It has been known that in a CDI process, a carbon aerogel electrode can remove heavy metals, colloids and the like, as well as ions.
By the way, the biggest problem involved in constructing an electrode for a capacitive deionization process using carbon aerogel or other carbon materials as an electrode material is that the surface of those materials are hydrophobic, and thus they rarely have wetting ability to an aqueous electrolyte. Therefore, in order to use a carbon material for an electrode for deionization process in an aqueous electrolyte, it is necessary to be used in great quantities. However, carbon aerogel, carbon nanotube and the like are expensive because a very small amount thereof is obtained in a single preparation. Therefore, if concentration of ions to be removed in a solution is high, there is a difficulty in using them.
Moreover, when an electrode is prepared only with a carbon electrode material, as charging and discharging are repeated, mechanical strength of the electrode active material becomes weaker, and thus, the electrode active material is separated from the electrode so as to reduce its lifetime.
Therefore, in order to use carbon materials for an electrode for a deionization processing apparatus, it is necessary to modify its physical properties.